With growing worldwide awareness of environmental issues, the control of the amount of hydrocarbon vapor emission from an automotive fuel hose or the like has been enhanced. Particularly in the United States, stringent regulations against vapor emission have recently come into effect. To cope with hydrocarbon vapor emission control in this situation, multilayer hoses have been proposed which include an intermediate layer composed of a fluororesin.
Such a multilayer hose employing the fluororesin is excellent in fuel permeation resistance to gasoline containing alcohol such as methanol and ethanol. To satisfy a stricter fuel permeation resistance requirement, the thickness of the fluororesin layer should be increased, resulting in correspondingly higher costs of the hose.
Polyphenylenesulfide (PPS) resins, which are better in fuel permeation resistance than the fluororesin, are attractive. Such a PPS resin has excellent fuel permeation resistance and, therefore, a layer composed of the PPS resin has satisfactory permeation resistance even if having a relatively small thickness. Accordingly, a hose including an intermediate layer composed of the P resin is more advantageous in costs than a hose including the intermediate layer of the fluororesin. As an example of the hose including the intermediate layer of a PPS resin, a fuel hose has been proposed which includes an intermediate layer of a PPS resin and a layer of a non-PPS thermoplastic resin (polyamide resin or the like) provided on an outer peripheral surface of the intermediate layer (see, for example, JP-A-2008-111063).
In the fuel hose disclosed in JP-A-2008-111063, an adhesive layer composed of a composition containing a PPS resin, a polyamide resin, a thermoplastic resin having a functional group and an uncrosslinked elastomer is provided between the layer of the PPS resin composition (PPS resin layer) and the layer of the polyamide resin composition (polyamide resin layer) to bond the PPS resin layer and the polyamide layer. However, interlayer adhesiveness between the PPS resin layer and the polyamide resin layer is disadvantageously poor, because the PPS resin layer and the polyamide resin layer of the fuel hose are merely bonded to each other due to the affinity of the PPS resin layer for the PPS resin in the adhesive layer and the affinity of the polyamide resin layer for the polyamide resin in the adhesive layer. Further, the PPS is excellent in fuel permeation resistance, but poor in flexibility. Therefore, the fuel hose disclosed in JP-A-2008-111063 is disadvantageously poor in flexibility, because the PPS resin layer is provided as the intermediate layer and, in addition, the adhesive layer contains the PPS.